Electric selection controlling circuit



2 She'ets-Sheet 1 Hill H. F. HERBIG ELECTRIC SELECTION CONTROLLING CIRCUIT Filed May 6, 1943' Aug. l, 1944.

Aug. l, 1944. H. F. HERBIG ELECTRIC SELECTION CONTROLLING CIRCUIT'.

Filed May 6, 1943 2 Sheets-Sheet 2 SELECTOR REGITER Patented Aug. l, 1944 TION CONTROLLING ELECTRIC SELEC IRCUIT Henry F. Herbig, Madison, N. J., assignor to International Standard Electric Corporation, New York, N. Y., a corporation oi' Delaware Application May 6,1943, Serial No. 485,827

17 Claims.

This invention relates to new and useful lmprovements in selection control circuits and more particularly to circuits for controlling the numerical selecting operation of selector` switches employed in automatic telephone exchange systems.

tures of the present invention, as is necessary for a clear understanding thereof.

In an automatic telephone system calling and called subscribers stations I and 2 (Fig. 1) may be inter-connected by means including a plurality of selector switches 3 and 4. The numerical operations of the selectors are controlled by the calling subscribers customary impulse sender or other number indicating device through the agency of a register provided at the central exchange. The calling station I is connected t0 the brushes of selector 3 by non-numerical switches and a connecting circuit 6, and the register is attached to the connecting circuit 6 through switching means 5.

The selector switches are of the customary type having a bank of terminals with which a set of brushes cooperates. In the drawings three brushes are shown for selector 3 although the selector may have a larger number of brushes. The selector brushes are moved over the terminals while a magnet P is energized and are stopped on a set of terminals when this magnet becomes deenergized.

The register comprises a series of switches successively operable by the calling device in accordance with the successive digits of the called number. A brush and a set of terminals of one of these register switches is shown in Fig. 1. This is the register switch which responds to the digit destined for selector 3. When brush RB is advanced towards one of ten terminals (only four of which are shown) in accordance with the operation of the calling device' atthe station i, the register starting relay RSR, having been energized in the customary manner, a circuit isclosed from ground over the armature and back contact of a relay GVR in the register, the armature and front contactfof relay RSR in the register, the

contacts of preceding selectors, the winding of a selector relay AR, to grounded battery. yAR operates and closes a parallel energizing circuit for the selector magnet P. In its back contact AR removes the normal ground from the selector to brush T.

The magnet P starts the brushes of the selector 3 to move over the terminals and will continue until GVR becomes1 energized.

The energization of relay GVR is controlled by a gas valve GV having a cathode C, an anode A and a control electrode CE. The control electrode CE is connected over a 200,000 resistance R5 and a 300,000w resistance R3 with a high tension battery HTB. The anode A of the gas valve is connected over a 1000e resistance R6 and the winding of relay GVR with battery. The cathode C being grounded, the relay GVR will be enerwhich the screen grid is connected with the cathode. Triodes having suitable characteristics could be used but the employment of tetrodes in the manner described enables smaller voltage steps to be employed. Tetrodes of the type RCA.50L6GT have been used and enable the system to operate satisfactorily when their filaments are run at about half their rated voltage. two tubes may be provided within the same bulb or in separate bulbs. The gas valve GV may be of any commercial type, the one disclosed being of the customary three-electrode cold cathode type.

Various potentials may be applied to the electrodes of VI and V2 over register brush RB and selector brush T. The potentials applied to the grid of the n rst tube VI and the cathode of the second tube over register brush RB and the potentials applied over selector brush T to the cathode of the ilrst tube VI and the control grid of the second tube V2 are indicated in Fig. 2. The

. potentials in the selector are applied over 600w resistances R1 vand those in the register over l 100e resistances R8. The control grids are con- The l Plate circuits which leads to the high tension battery HTB. The control electrode CE of the gas valve GV connected with this common branch is kept below the potential necessary for the ionization ofthe gas valve. However, when both control grids have the same potential as their respective cathodes, then the current flowing in this common branch ot the plate circuits will not be appreciable and the potential of the control electrode CE will rise to the lull potential of the high tension battery. thus causing the gas valve GV to ionize and operate the relay GVR. I

When the relay GVR operates, it opens in its back contact the energizing circuit of the selector power magnet P stopping the selector on the test terminals of the line to which the same negative potential is connected as to the terminal on which the register brush RB is resting.

The establishment of the complete connection is continued in the same manner.

The brush RB remains in contact with a terminal when it first touches the next terminal thus momentarily bridging two terminals, which will prevent the opening of the connections to the cathode of V2 and control grid of VI. 'I'he selector brush T cannot be arranged to bridge two terminals, since the selector terminals are multipled. To guard against false operation of tubes VI and 'V2 when brush T leaves a terminal, the circuit leading to this brush is grounded over a l megohm resistance-R4.

In Fig. 3, an arrangement is disclosed in which only two triodes are used in the register, the gas valve being eliminated. Instead oi' distinguishing between the terminals engaged by the register and the selector brushes by only voltage differences, the distinction is made both by voltage and polarity dillerences. Thus, the iirst iive terminals of both the register and the selector may be connected to 6, 12, 18', 24 and 30 volt taps oi' negative battery and the second group `oi' ilve terminals to similar taps of vpositive battery. The adjacent terminals may be graded by other than 6 volt steps.

When the selector brush T is hunting over test terminals the potential of which is more negative than the potential applied to the terminal on which brush RB is resting, then the control grid of tube VI which is connected with brush T over a resistance R3 will be more negative than the cathode of this tube which is connected with brush RB over a resistance R2. tube V2 which is connectedwith brush RB and 7 with the grid of VI by a resistance RI will, therefore, be positive with respect to the cathode of this tube which is connected with brush T of the selector. While this condition prevails. the plate current of tube VI will be substantially zero and the plate current of tube V2 will be at its saturation value causing the closing of an energizing circuit for relay VR! over the high tension battery to ground over the front contact and armature oi' a relay X in the register which is energized at that time.

If the conditions were reversed as to the relative polarities ofthe terminals with which the two brushes are in engagement, then the relay VRI would become energized and the relay VR2 remain de-energized.

While one or both these two relays remain deenergized the circuit of the power magnet P of the selector (which, as in the previous case was established over armatures and front contacts of relays AR and RSR) will also remain closed 'I'he grid of matassa l l relay VRI operates. It during this short transmit time the selector magnet P should release before VR2 applies its holding ground through its back contact. then a condenser'C may be used between the break springs oi relays VRI and VR2 and ground. The charging current owing through. this condenser would keep' the magnet P oi' the selectors energized until the ground is restored at one of the relay contacts.

When the brush T of the selector contacts with a terminal that has the samel potential and polarity of the terminal on which the register brush is resting, then the grids o! the two tubes VI and V2 will be at the ysaine potential as their respective cathodes, i. e. at substantially zero potential. No current can now over Ri. The plate circuit of each tube will reach the saturation point and both relays VRI and VR2 will be operated at the same time. This will remove ground from the circuit oi' the power magnet P and the selector will be stopped with its b brushes on the terminal selected.

Upon the operation of relays VRI and VR2,

a short-circuit is closed over the inner iront con-` brush T of the selector is momentarily grounded for a busy condition.

The resistance RI may have a value of l megohm or more which will eliminate any in duction interference that might be produced during the hunting of the selector brush T over its terminals. Resistances R2 and R3 which are connected in series with those brushes may be 100G-2000a so as to limit the current to less than .020 ampere during the short time a busy ground over the back contact of relay AR is applied to brush T. HTB is a high tension battery of approximately 100 volts.

Here as in Fig. l the test conductor is grounded over resistance R4, which may be provided in the register or the selector.

In the arrangement shown in Fig. 4, the two Vacuum tubes VI and V2 are used in conjunction with a four-rectifier bridge and a single winding quick releasing relay VR or, as shown in Fig. 5 a double wound relay VR and two rectiiiers SI and S2.

The two triodes VI and V2 have the characteristic that the plate currentv is more or less proportional to the grid potential and polarity. Only when the grids of the two tubes are at the same potential and have the same polarity will the plate currents and plate potentials of the two tubes be equal.

When the plate potentials are equal then current ilows from the high tension battery HTB over an armature and front contact oi.' the register relay RSR (this contact is-for the sake of clarity shown as mechanically separated from the relay) and thence through the resistances shift of the controlling potential from VI to V2 or vice versa, will not cause VR to release.

When RB is advanced to a terminal and the relay RSR is energized, unequal current will flow since the grid of tube V2 will find a ground applied over the armature and back contactof the selector relay AR. When the AR becomes energized then ground is applied to this grid over resistance R4. It will be noted that the ground applied through the armature and back contact of relay AR cannot reach the register brushes RB except through the very high resistances Rl and R4 When'the test brush T reaches the terminal that has the some polarity as the terminal onwhich RB is resting, then no current will flow through relay VR. This relay releases and opens the energizlng circuits of relay AR and power magnet P thus stopping the selector.

The current flow over the test wire during selection is so small that it does not tend to develop cross-talk. The arrangement of the battery connections to the selector and register terminals is the same as in Fig. 3.

ond tube, and the second contact of the selector is connected to the cathode o! the first tube and the grid of the second tube.

5. The combination of claim 1, and in which a gas valve is provided between said tubes and said relay means.

6. The combination of claim l, and in which said relay means comprises two relays, one connected with the anode of each tube, the circuit of the selector magnet being controlled over back contacts of said relays in parallel.

y adapted successively to engage them, means for This arrangement permits the use of directly heated cathodes whereby the filament circuit may be open when the register is idle without fear of delay when the register is subsequently picked up and the nlament circuit is again closed. Directly heating filaments go into an emitting condition a1- most instantly after the closing of the lament circuit.

What is claimed is:

1. In combination, a selector switch having a -plurality of first contacts and a second contact a magnet for controlling the contacting of the second with any first contact, a register having a plurality of first contacts and a second contact, means for contacting the second register contact with any first contactv of the register, a control circuit extending from said register to the magnet of said selector, relay means in said register for controlling said circuit, two vacuum tubes in said register each having a cathode, a grid and an anode electrode, a connection from the second register contact to one electrode of the iirst tube, a connection from the second selector contact to the corresponding electrode of the second tube, a source of potential, connections for applying different potentials to each first contact of the register and selector. and a circuit for operating said relay means jointly controlled by said vacuum tubes.

2. The combination of claim 1 and in which said source is a source of D. C. potentials, and said connections from the second contacts of the .register and selector are to the grids of the two tubes.

3. The combination of claim 1 and in which the potentials applied to the rst contacts of the register are the same as those applied to those of the selector, and the vacuum tubes cause the op-` eration of the relay means if contact is made in thselector with a first contact to which the same potential is applied as to the rst contact with which thesecond contact of the register is in engagement.

4. The combin tion of claim 1, and in which said source is a source\of D. C. potentials, the second contact of the register is connected to the grid of the rst tube and thethode of the seccontrolled by said vacuum tubes.

7. The combination of claim l, and in which the relay means consists of a relay having a contact controlling the circuit of the selector magnet, and in which direct current potentials are connected over the second contacts of the register and selector to the grids of the tubes, an energizing circuit for said relay including the anodes of said tubes, and rectifiers in said energizing circuit.

8. In combination, a vselector switch having a plurality of terminals and a set of cooperating brushes, a magnet for controlling the operation of said brushes, a register comprising a switch having a plurality of terminals and a brush operating the register brush to engage any terminal, a control circuit extending from said register to the magnet of said selector, relay means in said register for controlling said circuit, two vacuum tubes in said register each having e. cathode. a grid and an anode, a connection from the register brush to the grid of the first tube` a connection from the selector brush to the grid of the second tube, a source 0f D. C. potential, connec- 'tions for applying the same potentials to the terminals of the register and selector switches, there being a predetermined voltage difieren-ce between the potentials applied to adjacent terminals, and a circuit for operating said relay means jointly 9.-'Ihe combination according to claim 8 and in which said connection from the register brush includes also the cathode of the second tube and said connection from the selector brush to the cathode of the first tube.

10. In combination, a selector switch having a plurality of terminals and a set of cooperating brushes, a magnet for operating said brushes, a register comprising a switch having a plurality of terminals and a brush adapted successively to engage them, means for operating the register brush to engage any terminal, a control circuit extending from said register to the magnet of said selector, a relay in said register for confrom the selector brush to the grid of the second tube and the cathode of the first tube, a source of D. C. potential, connections for applying the same potentials to the terminals of the register and selector switches, there being a predetermined voltage difference between the potentials applied to adjacent terminals, and a connection from the anodes of the two tubesin multiple to the control electrode of the valve.

11. In combination, a selector switch having a plurality of terminals and a set oi cooperating brushes, a magnet for operating said brushes, a register comprising a switch having a plurality oi terminals and a brush adapted successively to engage them, means for operating the register brush t engage any terminal, a control circuit extending from said register to the magnet of said selector, a relay in said register for controlling said circuit, a grounded high tension battery, a gas valve having a control electrode connected with said battery, a grounded cathode and an anode connected over the winding oi' said relay with said battery, two vacuum tubes in said register each having a cathode, a control and a screen grid and an anode, a connection from the register brush to the control grid oi the ilrst tube and the cathode and screen grid of the second tube, a connection from the selector brush to the control grid of the second tube and the cathode and screen grid oi' the first tube, a source oi' D. C. potential, connections for applying from said source potentials of the same voltage and polarity to the terminals of the register and selector switches, there being a predetermined voltage difference between the potentials applied to ad... jacent terminals, and a connection from the anodes of the two tubes in multiple to the control electrode oi the gas valve.

12. In combination, a selector switch having a plurality of terminals and a set oi' cooperating brushes, a magnet for operating said brushes, a register comprising a switch having a plurality of terminals and a brush adapted successively to engage them, means for operating the register brush to engage any terminal, a control circuit extending from said register to the magnet of said selector, two relays in said register each having a contact for controlling said circuits, two vacuum tubes in said register each having a cathode, a grid and an anode, a connection from the register brush to the grid of the iirst tube and the cathode of the second tube, a connection from the selector brush to the grid oi' the second tube and the cathode of the rst tube, a source of D. C. potential, connections for applying the same potentials to the terminals ofthe register and selector switches, negative potentials to some and positive potentials to other terminals, there being a predetermined voltage difference between the potentials applied to adjacent terminals, acircuit for operating one relay including the anode of the rst and a circuit for operating the other relay including the anode of the second tube.

13. In combination, a selector switch having a plurality of terminals and a set of cooperating brushes, a magnet for operating said brushes, a register comprising a switch having a plurality of terminals and a brush adapted successively to engage them, means for operating the register brush to engage any terminal, a relay for said register having a contact controlling the selector magnet, two vacuum tubes in said register each having a cathode, a grid and an anode, a connection from the register brush to the grid of the first tube, a connection from the selector brush to the grid oi the second tube. a source of D. C. potential, connections for applying the l same potentials to the terminals of the register and the selector switches, positive to some and negative to others, there being a predetermined difference between the potentials applied to 4adjacent terminals, an energizing circuit for said relay connected to the anodes of both tubes, and rectiilers in said bridge allowing the now of current over said relay only in one direction.

14. An electrical control system comprising a selector device having a contact brush, actuating means for moving said brush successively over a plurality of positions, means i'or applying a characteristic potential to said brush in each of said positions, control means for controlling said actuating means. an electron discharge means including ilrst and second electron discharge paths each comprising a cathode, an anode and a control grid electrode, a connection from said brush to said control grid electrode of said first path and cathode of said second path, means for applying a predetermined potential to the control grid electrode o said second path and the cathode of said rst path and a connection from said two anodes in parallel to said control means,

15. An electrical control system according to claim 14 wherein each said discharge path also comprises a further grid electrode located between the respective control grid electrode and anode and directly connected to the respective cathode.

16. A switching arrangement for a telecommunication system comprising a register switch having a plurality of contacts and a cooperating contact brush, means for applying a characteristic potential to each of said contacts, means for operating said register brush to engage any said contact, a selector switch having a plurality of contacts and a cooperating contact brush, means for applying a characteristic potential to each of said selector contacts, actuating means for controlling the movement of said selector brush over its contacts, a control device for said actuating means, an electron discharge means including iirst and second discharge paths each comprising a cathode, an anode and a control grid electrode, a connection i'rom said register brush to the control grid electrode of said first path and the cathode of said second path, a connection from said selector brush to the cathode of said rst path and the control grid electrode of said second path, and a connection from said two anodes in parallel to said control device.

17. An electrical control system according to claim 16 wherein each said discharge path also comprises a further grid electrode located between the respective control grid electrode and anode and directly connected to the respective cathode.

HENRY F. HERBIG. 

